Bituminous polyurethane interpenetrating elastomeric network compositions as coatings and sealants for roofing and other applications

ABSTRACT

Elastomeric polyurethane interpenetrating network compositions are disclosed which are preferably developed by in situ reaction of polyols with different isocyanates and polyisocyanates in a bituminous material, such as, asphalt, coal tar, polymer modified asphalt, oxidized, and unoxidized asphalt. The composition is preferably formed at a temperature between 200° F. and 350° F. The reaction kinetics can be accelerated by including catalysts and curing agents. Bituminous polyurethane interpenetrating network elastomers are suitable for a wide variety of applications including but not limited to roofing, new construction, and wall and foundation waterproofing applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a continuation of U.S. patent applicationSer. No. 09/893,242, filed Jun. 27, 2001, which is a continuation ofU.S. patent application Ser. No. 09/377,093, filed Aug. 19, 1999, nowU.S. Pat. No. 6,271,105, issued Aug. 7, 2001, which claims the benefitof U.S. Provisional Application No. 60/097,158, filed Aug. 19, 1998 (allof the above-identified applications are incorporated by reference).

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to the in situ generation andincorporation of polyurethane prepolymers generated within a matrix ofbituminous material such as asphalt. The resulting bituminouspolyurethane interpenetrating elastomeric network compositions can beapplied as coatings and sealants for roofing, coverings, andconstruction waterproofing applications, as well as other applications.

[0004] 2. Description of Related Art

[0005] Polyurethanes are extensively used as coatings and sealants inhousing, construction, furniture, and other industries. Polyurethaneprepolymers are generally developed by reacting different polyols withdi- or poly-isocyanates in varying ratios. FIG. 2 depicts a reactionbetween a polyol and diisocyanate. Polyurethanes are hard,water-resistant, slippery when wet, and tend to degenerate when exposedto ultra-violet light.

[0006] “Bituminous material” is meant to include bitumen, asphalt, coaltar, and performance-rated asphalt. Due to the low cost of bituminousmaterial, its relatively high penetration value when applied to mostporous surfaces, weather-resistant nature, and impermeability to water,bituminous material has traditionally been used as a main component ofprotective films, adhesive binders in asphalt emulsions (M. Lalanne andJ. Serfass, U.S. Pat. No. 4,724,245), in blends used for paving androofing, joint sealants, paints, and other end uses. Existingunreinforced bituminous materials tend to crack during normal seasonalthermal expansion. In addition, typical bituminous materials aredifficult to apply and take a long time (days) to cure completely.

[0007] Attempts to provide a blend of a liquid, preferably anambient-curable prepolymer, with bituminous material have been made (H.Lucke, U.S. Pat. No. 4,871,792). In the past, several methods weredeveloped to increase the compatibility between the bituminous binderand polyurethanes, either by using a modified clay (R. J. Janoski, U.S.Pat. Nos. 5,421,876 and 5,319,008), or pre-treating the bituminousmaterials before mixing with polyurethane prepolymer (M. Shihadeh, U.S.Pat. No. 3,980,597).

[0008] Several attempts to develop a rubberized bituminous materialusing crumb rubber have also been made. Methods are available, reported,and in practice today. Crumb rubber from recycled car and truck tiresimproves wear resistance (D. W. Causyn and K. Thys, PCT Int. Appl. WO9221820), lowers temperature fracture properties (G. R. Morrison and S.A. M. Hesp., J. Mater. Sci. 30(10), 2584 (1995) and A. Coomaraswamy, S.Manolis and S. Hesp., Am. Chem. Soc. Div. Fuel. Chem., 41(4), 1322(1996)); and enhances coating performance and safety of the coatedsurface (M. Wm. Rouse, Rubber World, 212(2), 23 (1995)). Most of theseapplications are used in the paving industry, anti-skid mats forplaygrounds, and running tracks (H. L. Draper, D. F. Levy, and D. W.Gagle, U.S. Pat. No. 3,547,674).

[0009] Apart from the use of crumb rubber, other polymers are used tomodify asphalt (M. E. Labib, G. M. Memon, and B. H. Chollar, Prepr.Pap.—Am. Chem. Soc., Div. Fuel. Chem., 41(4), 1209 (1996), I. K.Negulescu and W. H. Daly, Annu. Tech. Conf., Soc. Plat. Eng. 54th (vol.1), 1175 (1996). The thermoplastic nature of these existing polymermodified bituminous materials limits their coating and sealantapplications.

[0010] These past attempts to incorporate a resin within a bituminousmaterial have failed for a combination of reasons. First, polyurethanesand bituminous materials are not miscible because polyurethanes arepolar, while bituminous materials are non-polar. Second, without more,the reaction rate between the reagents forming the polyurethane (polyoland isocyanate) is slow enough that the reagents separate from thebituminous material, polymerize, and form non-integrated, heterogeneousproducts. These heterogeneous products do not produce synergisticqualities such as increased strength and ease of application.

BRIEF SUMMARY OF THE INVENTION

[0011] Owing to the advantages of polymer modified bituminous materials,this invention is a further novel modification of bituminous materialswith polyurethanes, by in situ generation of their prepolymers, so thatthe prepared bituminous polyurethane interpenetrating elastomericnetwork compositions will be stronger, easier to apply, and lessexpensive than the conventional mixing of polyurethane prepolymers withbituminous material. The mixing of polyurethane prepolymer with therubberized bituminous material at the molecular level results fromimproved miscibility. In turn, improved miscibility improves thephysical and mechanical properties of the coatings and sealants.Suitable bituminous materials include, but are not limited to, asphalt,coal tar, polymer modified asphalt, oxidized, and unoxidized asphalt.

[0012] According to the method of the invention, the polyol andbituminous materials are mixed separately from the isocyanate. Thepolyol and molten bituminous material are more miscible thanprepolymerized polyurethane and bituminous material. Next, a catalystand curing agent can be added to either of the polyol or isocyanate. Thepolyol/bituminous material mixture is then mixed thoroughly with theisocyanate immediately before application. The catalyst causes thepolyurethane to form rapidly (in as little as seconds) within thebituminous material to form an effectively-homogenous, three-dimensionalmatrix.

[0013] The properties of the resulting matrix can be controlled bychanging the formulation. By increasing the proportion of cross-linkingagents such as diisocyanate, the strength of the product is increased.By reducing the proportions of cross linking agents, the flexibility ofthe materials can be increased. Increased strength is useful inapplications such as building reinforcement. Increased flexibility isuseful in applications such as coating a running track or manufacturingo-rings.

[0014] A curing agent can be added to decrease the time before apermanent matrix is formed. Curing agent can reduce the gelation time toas little as seconds. Reduced gelation time is useful to expedite thecompletion of jobs such as filling cracks and crevices. A curing agentcan be omitted or limited in situations requiring a longer time beforesetting. A longer setting time can be desirable when the material isused as an adhesive and time is required to position the materials beingadhered.

[0015] These materials were tested as coatings, sealants, and adhesiveson a range of substrates. These materials can be generated at the jobsite, and are applied to various surfaces, through our uniquely designedpumping, metering, mixing, and spraying system.

[0016] The present invention achieves the additional advantages setforth below by providing a unique method of modifying polyurethanes intouseful compositions which meet the essential requirements for coatingsand sealants. The asphalt/bitumen components provide processability ofthe resultant coatings and sealants. The rubber component providesfrictional and abrasion resistance as well as ultra-violet radiationresistance to the coatings and sealants. The unique method of producingthese polymers yields easy applications as well as an -overall decreasein the coating cost.

[0017] The bituminous polyurethane interpenetrating elastomeric networkcompositions produced have improved adhesion. The highly reactiveurethane prepolymer gives better adhesion to different substrates. Thecoated substrates were evaluated for their physical and mechanicalproperties, adhesion, static and dynamic puncture resistance, wind-uplift test, and other properties. Bituminous polyurethaneinterpenetrating network elastomer compositions of the invention areresistance to solvents, oil, and acid.

[0018] The reaction kinetics were followed by measuring the torqueincrease as a function of reaction time. The gelation time is measuredat the maximum torque. For testing, the bituminous polyurethaneinterpenetrating network elastomeric compositions werehot-sprayed-applied (200° F.-350° F.) on different substrates such asconcrete, metal, wood, built-up roofing systems, polyurethane foams, andother construction materials with a specially designed spray applicatorsystem. The present invention composition is preferably formed, througha melt polymerization process, such as an in situ melt polymerizationreaction. The composition is preferably solventless and fillerless.

[0019] Therefore, an object of the present invention is to provide acomposition which is superior in providing coating and sealing over asubstrate.

[0020] Another object of this invention is to provide a method ofpreparing such a composition at or near the site of application, easilyand economically.

[0021] Another object of this invention is to provide a sealing andcoating composition which provides superior traction performance.

[0022] In accordance with these and other objects which will becomeapparent hereinafter, the instant invention will now be described withparticular reference to the accompanying drawing.

BRIEF DESCRIPTION OF THE FIGURES

[0023]FIG. 1 is a schematic representation of the process of the instantinvention;

[0024]FIG. 2 is a prior-art chemical reaction depicting the formation ofa typical polyurethane prepolymer from a polyol and diisocyanate;

[0025]FIG. 3 is a table summarizing a series of controlled experimentscontaining different formulations;

[0026]FIG. 4 is a table summarizing a series of controlled experimentsutilizing different curing agents;

[0027]FIG. 5 is a table summarizing a series of controlled experimentsutilizing different bituminous materials;

[0028]FIG. 6 is a perspective view of a mobile apparatus for thepreparation of a bituminous polyurethane interpenetrating elastomericnetwork composition; and

[0029]FIG. 7 is a table listing a most preferred embodiment of thecomposition at the time of filing.

DETAILED DESCRIPTION OF THE INVENTION

[0030] Polyurethanes are widely used as coatings as well as sealantcompounds because they adhere to a variety of substrates, resistscratching, and resist moisture. However, their uses are limited due tothe high cost associated with application, degradation caused byultra-violet light exposure, and slipperiness. The several compositionsdeveloped in the present invention are useful for convertingpolyurethanes into coatings as well as sealant compositions by a meltblending process. The first step includes the premixing of polyol(s)with the bituminous material already at its molten temperature to form areagent mixture. The reagent mixture is carried separately from theisocyanate to the mixing head by heated hoses. At the mixing head, thereagent mixture and isocyanate are mixed. The polyurethane prepolymerforms as the reagent material and isocyanate mix. These materials aremetered through a narrow metallic tube for sufficient molecular weightbuildup and sprayed under pressure through a suitable spray apparatus.

[0031] Applications of the invention include the use of:

[0032] bituminous materials such as asphalt, polymer and rubber enrichedperformance grade asphalt, and coal tar;

[0033] new and recycled crumb rubber and synthetic rubber;

[0034] polyols such as PPG (polypropylene glycol), PEG (polyethyleneglycol), POTMG (polyoxytetramethylene glycol), HTPD (hydroxy terminatedpolybutadiene), castor oil, and vegetable oils of different molecularweight and functionality; and

[0035] isocyanates such as polymeric MDI as well as other dimeric andpolymeric isocyanates.

[0036] In each of the following examples, the products were prepared ina common related manner. The bituminous material was prepared bydegrading and dissolving crumb tire rubber in hot mix asphalt and heatedto at least the molten temperature of the asphalt. The crumb rubbercontent in the asphalt component was between zero and seventy-fivepercent (0-75%) by weight. The rubberized asphalt was preheated between125° C. and 225° C. in a separate vessel and this mixture is calledcomponent A. The polyol, either single or in combination of more thanone, was catalyzed preferably with dibutyltin dilaurate (1-5% of thepolyol weight) with constant stirring in a separate vessel and is calledcomponent B. The isocyanate (dimeric and polymeric either alone or incombination) was placed in another separate vessel and is calledcomponent C. All three components were metered at varying compositions,mixed immediately before spraying, and the resultant composition sprayedonto different substrates. The substrate may be any type of concrete,wood, metal, rubber, asphalt, or other commonly used roofing material.

EXAMPLE 1

[0037] Components B and C were mixed to form the polyurethaneprepolymer, and the resultant composition was then mixed with componentA in situ and then sprayed on a pre-fabricated aluminum dye at differentthicknesses (e.g. 2 mm, 4 mm, 6 mm, etc.). The resulting bituminouspolyurethane interpenetrating elastomeric network composition was thenallowed to cure for twenty-four hours at 25° C. and post-cured for fivedays at 25° C. All the samples were die cut for different testspecimens. The viscosity, stress-strain properties, and other physicaland mechanical properties should be tested in accordance with proceduresset forth in ASTM D 412.

EXAMPLE 2

[0038] By the same procedure, rubberized asphalt made from rubbersources, was used including virgin rubbers (styrene-butadiene rubbers,butadiene rubbers, butyl rubbers, EPDM rubber (ethylene propylene dienemonomer), natural rubber, rubber made from other block copolymers andpolymers of similar nature) and waste rubbers from other resourcesincluding off-specification rubbers and off-specification compounds fromcompounding operations.

EXAMPLE 3

[0039] By the same procedure as Example 1, the component B wassubstituted with other polyols, polyester polyols of different types anddifferent molecular weight, polyether polyols of different types anddifferent molecular weights, polyol substitutes from vegetable oils suchas castor oils and oils of similar nature. These components were eitherused alone or in combination with each other.

EXAMPLE 4

[0040] By the same procedure as Example 1, the component C wassubstituted with other di and/or polyisocyanates.

EXAMPLE 5

[0041] By the same procedure as Example 1, the catalyst was substitutedwith others.

EXAMPLE 6

[0042] By the same procedure as Example 1, the different ratios ofcomponents B with components C are tested.

EXAMPLE 7

[0043] By the same procedure as Example 1, the reactions were tested atdifferent temperatures.

EXAMPLE 8

[0044] By the same procedure as Example 1, the reactions were carriedout in different residence time (reaction time) and the materials testedfor their physical and mechanical properties.

EXAMPLE 9

[0045] By the same procedure as Example 1, the coating is applied insequence to study the colorability, and compatibility is tested.

EXAMPLE 10

[0046] Several selected formulations were sprayed on several substrates,including wood, metals, concrete, bricks, rubbers, asphalt binders, andsubstrates of similar nature. The adhesion between these coatings andthese substrates is measured by measuring the peel strength.

[0047] A series of controlled experiments were conducted to determinethe effect of varying the formulation of the composition. The results ofthese experiments are listed in FIGS. 3, 4, an 5. In these experiments,unless specifically stated, the following methods were used. First, arequired amount of asphalt was placed in a one quart (1 qt) tincontainer. The container was placed in an electric heating mantel. Thedesired temperature was maintained using a controller having an accuracyof plus or minus three degrees Fahrenheit (±3° F.) The temperature ofthe liquid contents in the container was monitored by a sensor immersedin the liquid asphalt mixture. The mixture was mixed using a stirrer.The stirrer utilized an overhead motor with a digital display of speedand torque. Torque was used to measure the viscosity of the mixture. Thetorque was monitored throughout the duration of the reaction. In theexperiments, the polyol was preheated. If any curing agent or catalystwas included, they were added to the polyol. The polyol was then addedto the asphalt and mixed for twenty minutes (20 min). The isocyanate wasadded gradually (1-3) seconds to the mixture. The gelation point wasdetermined from the plot of time versus torque. Each experiment wasrepeated to verify the reproducibility and accuracy of the results.

[0048] Polyols

[0049] The following polyols are applicable to this invention: polyetherpolyols, polyester polyols, hydroxyl terminated polybutadiene and theircopolymer with acrylonitrile, cicinoleic triglyceride (commerciallyknown as “castor oil”), and other vegetable oils of similar nature withdifferent functionality and molecular weight.

[0050] A polyol which is particularly suited for use in the invention ispolypropylene glycol, with the below specifications: Hydroxyl numbermg/KOH/gm 102-115 Acid Number (Max.) 0.04 to 0.05 Unsaturation (meq/g,max.) 0.025 to 0.028 Functionality 2 Density lbs/gal @ 25° C. 8.00-8.50Viscosity, CPS @ 25° C. 75-80

[0051] The particular suppliers of this polyol include but are notlimited to BASF Corporation, USA and Dow Chemical Company, USA.

[0052] Isocyanates

[0053] Isocyanates which can be utilized with this invention includediphenylmethane diisocyanates (“MDI”), toluene diisocyanates (“TDI”),hexamethylene diisocyanates (HMDI”), and isophorone diisocyanates(“IPDI”). All of these have a functionality of two or greater.

[0054] An isocyanate which is particularly suited for use in thiscomposition is MDI, with the below specifications: Appearance Dark brownliquid NCO content, wt % 32-35 Viscosity @25° C., cps 70-75 Flash point° C. (COC) >200° C. Density @ 25° C., g/cm³ 1.2-1.3

[0055] Suppliers of this isocyanate include but are not limited to BASFCorporation, USA and Dow Chemical Company, USA.

[0056]FIG. 3 shows the results from a series of controlled experimentsthat show the impact of varying the amount of isocyanate. Formulation 1is a preferred embodiment containing ten percent (10%) by weightisocyanate. Formulation 6 contains only nine percent (9%) by weight ofisocyanate. By reducing the amount of isocyanate, the gelation of theproduct can be controlled.

[0057] Catalyst

[0058] Catalysts applicable to this invention include dibutyltindilaurate, dioctyltin dilaurate, different tertiary amines andorganometallic compounds of tin, lead, cobalt, and zinc.

[0059] A catalyst which is particularly suited for use in this inventionis dibutyltindilaurate (“Dabco T-12”), with the followingspecifications: Flash point ° C. (PMCC) >100° C. Viscosity @ 25° C., cps 125 Specific gravity at 25° C. 1.05 Water solubility Soluble AppearanceOily liquid Calculated OH Number, MgkOH/g   0

[0060] A supplier of this catalyst is Air Products and Chemicals, USA.

[0061]FIG. 3 is a table of experimental results showing the effect ofincluding a catalyst within the formulation. Formulation 1 is apreferred embodiment of the formulation and includes a trace amount ofcatalyst and four percent (4%) by weight of a curative agent.Formulation 1 produces an instantaneous induction time and a gelationtime of fifty (50) seconds. Induction time is the time required for theviscosity of the formulation to begin increasing as a result ofpolymerization. Gelation time is the time required for the viscosityeffectively to reach infinity. Formulation 2 demonstrates the effect ofnot including the catalyst: the induction time is sixty seconds and theviscosity of the formulation reaches a plateau after 210 seconds.

[0062] Curing Agent

[0063] Curing agents applicable to this invention are those generallyutilized with polyurethanes and specifically include the following:3,5-dimethythio-2,6-toluenediamine, 3,5-dimethylthio-2,4-tolunediamine,hexamethylene diamine, and trimethylol propane. In addition, theinvention includes those products sold under the following trade names:ETHACURE-100 and ETHACURE-300 both available from Albermarle; andJEFFAMINE-400 available from Huntsman. Thus, curing agents which can beused with the present invention include, but are not limited to,polyoxy(methyl-1,2,-ethanediol),alpha-hyrdoxyomega-(2-aminomethylethoxy)-ether with2-ethyl-2-(hydroxymethyl)-1,3-propanediol(3:1); diethyltoluenediamine;di-(methylthio)toluenediamine; 1,6-hexamethylene diamine; trimethylolpropane; 3,5-dimethylthio-2,6-toluenediamine;3,5-dimethylthio-2,4-toluenediamine, and other di and poly functionalamines.

[0064]FIG. 3 shows the results of a series of controlled experimentsdemonstrating the effect of curing agents. Formulation 1 shows apreferred embodiment of the invention. Formulation 3 a, b, and c showthe effect of increasing the curing agent from zero to six percent(0-6%) by weight. The inclusion of greater amounts of curing agentreduced both the induction time and the gelation time. However, abovefour percent (4%) curing agent, full gelation is never reached. Fromthis result, the conclusion that the high concentrations of curing agentbegin to interfere with the formation of high-molecular-weight polymers.Formulation 4 includes no catalyst and no curing agent. The result was aformulation having a delayed induction time and gelation time.

[0065]FIG. 4 is a table showing the effect on gelation time that thedifferent curing agents create. For purposes of forming a waterproofingmembrane, a gelation time of sixty (60) seconds is preferred. For otherapplications, different gelation times may be more desirable.

[0066] Bituminous Material

[0067] Bituminous materials are a broad class of carbon-rich materialsthat typically have a high penetration index number (“PIN”). Examples ofbituminous materials include the numerous grades of asphalt, performancegrade asphalt (also known as polymer modified asphalt), and coal tar.The bituminous material preferably has a penetration index number of 16and 195.

[0068] Asphalts can be described by their penetration index numbers.While all asphalts are included in this invention, experiments wereconducted on Type I, II, III, and IV asphalts having PINs ranging from16 to 37.

[0069] Performance grade asphalts also can be described by theirpenetration index numbers. While all performance grade asphalts areincluded in this invention, experiments were conducted on the followingtypes: 70/28, 64/28, 58/28, and 52/34 having PINs ranging from 65 to195.

[0070] Hot mix asphalt is an asphalt that is heated up to certaintemperatures so that certain additives can be incorporated into it,which creates a new composition. Preferably, the amount of rubberizedasphalt in the invention is 40%-60% by weight.

[0071] Polymer modified asphalt is an asphalt that is modified with theintegration of certain polymers, both virgin and recycled. Polymermodified asphalts improve the property, performance, and applications ofasphalt.

[0072] Different kinds of polymers integrated into the asphalt mayinclude polyethylenes, polypropylenes, polystyrenes, different block,graft, and random copolymers, virgin rubber, and rubber from crumbrubber.

[0073] Overall range of crumb rubber content or other polymer in theasphalt is zero to seventy percent (0-70%) by weight. The particularrange (preferred range) used in this invention is between five andtwenty-five percent (5-25%) by weight.

[0074] The polyol available for combinations in this invention arereferenced above. The different combinations of polyols will bequantitatively premixed, in any combination, and calculated amounts ofcatalyst are mixed to optimize the various compositions in meeting therequirements of the particular application. The polyol used in oneapplication of the invention is catalyzed polyol.

[0075] An example of the dibutyltindilaurate is sold under the trademarkDabco T-12 by Air Products and Chemicals, PA, USA. Details of Dabco T-12are contained in the attached Polyurethane Additives Product Bulletinwhich is incorporated by reference herein as though fully set forthherein. The preferred range used in this composition is from 0.001 to0.05 percent by weight.

[0076] The preferred isocyanate used in this composition is MDI,generally described above. The isocyanate is preferably between five andtwenty percent by weight of the composition.

[0077] A suitable rubberized asphalt used for this composition containscrumb rubber from recycled car and truck tires of particle sizes rangingbetween ten and eighty (10-80) mesh. A supplier of this material isBitumar, Inc., Canada.

[0078]FIG. 3 depicts a series of controlled experiments that show theeffect that the concentration of asphalt has on induction time andgelation time. As shown in Formulations 5 a, 5 b, and 1, as theconcentration of asphalt increases the gelation time increases. The dataalso shows that regardless of the asphalt concentration, the inductiontime remains instantaneous.

[0079]FIG. 3 also shows the effect of temperature on the reaction.Formulation 5 d was conducted at 100° F. while formulation 5 c wasconducted at 250° F. At the higher temperature, the product containingno asphalt never fully gelled. In contrast at 100° F., the formulagelled after only 15 seconds.

[0080]FIG. 5 shows the results from a series of controlled experimentswherein the type of asphalt is changed to demonstrate its effect ongelation time. By changing the type of asphalt, the gelation time can becontrolled for different applications. Greater gelation times may beuseful in applications such as adhesives. Partially gelled products canbe used as elastomers for O-rings.

[0081] Application of Composition to Substrate

[0082] The procedure for application of the invention involves foursteps: a) pumping; b) metering; c) polymerization; and d) spraying(collectively referred to as “Process”), shown schematically in FIG. 1.

[0083] (a) Pumping Step

[0084] The raw materials, isocyanate (“I”), polyol (“P”), catalyst(“C”), and rubberized asphalt (“RA”) are pumped or supplied to themixing apparatus 20. P and C are premixed at mixer 22 and suppliedtogether as one component (“PC”). I and RA are supplied as the other twocomponents. PC, I, and RA are supplied directly from their containersthrough heated hoses 24, 26 and 28 connected to feed pumps 25, 27 and29, respectively in varying amounts or ratios as governed by controller40.

[0085] (b) Metering Step

[0086] The raw materials as received into the mixing apparatus areregulated by computerized controller 40, flow meters measuring 30, 32and 34, and thermocouples 35, 37 and 39 measuring the temperatures.

[0087] (c) Polymerization Step

[0088] The raw materials RA, I and PC are supplied to the mixingapparatus 20 where the in situ polymerization reaction is initiated bymixing the materials intensely so that a three-dimensional,semi-interpenetrating network molecular structure formation begins. Thisreaction process continues while the mixture flows from the mixingchamber 20 to the conduit 50, where polymer propagation takes placewithout allowing complete cross-linking. The entire apparatus ispreferably heated so as to accelerate the reaction rate and maintain thecomposition at the desired temperature. The resulting prepolymer isconveyed from the reaction chamber to the spraying device 80.

[0089] The preferred amount of polyurethane prepolymer in the inventionis between thirty and fifty (30%-50%) by weight. It should be noted thatthe entire apparatus shown in FIG. 1 is preferably heated, including allsupply lines and mixing chambers, so that the ingredients and resultingcomposition are maintained at a temperature in the range of 300° F.-340°F.

[0090] The preferred ratio of polyol/isocyanate to rubberized asphalt is50:50. The preferred ratio of polyol to isocyanate is 80:20. Thecatalyst is 0.07% by weight of the polyol composition.

[0091] (d) Spraying Step

[0092] The prepolymer 70 travels to the spraying device 80, where it issprayed out of a nozzle and onto the surface or substrate S to becoated.

[0093] Varying the Compositions

[0094] Depending upon the application, required amounts of all of theraw materials will be processed through the above-described process andapplied to the different substrates. The properties of the composition,nature of the substrates, application conditions, and other relatedfactors determine the resulting coating.

[0095] The prepolymers created by this invention will have reactiveisocyanate terminal groups and will cure with moisture and/or anymolecules with active hydrogen atoms. The overall range of thepolyurethane prepolymers is between ten and ninety percent (10%-90%) byweight.

[0096] In one embodiment the bituminous polyurethane interpenetratingelastomeric network composition can include: (a) fifty percent by weightof rubberized asphalt having a penetration index number of 30; (b)thirty-six percent by weight of polyether polyol; (c) four percent byweight of a blend consisting of 3,5-dimethylthio-2,6-toluenediamine and3,5-dimethylthio-2,4-toluenediamine; (d) a trace amount of dibutyltindilaurate; and (e) ten percent by weight of polymeric MDI.

[0097] The instant invention that has been shown and described herein isconsidered to be the most practical and preferred embodiment. It isrecognized, however, that departures may be made therefrom within thescope of the invention and that obvious modifications will occur to aperson skilled in the art.

What is claimed is:
 1. A bituminous polyurethane interpenetratingelastomeric composition comprising: a bituminous material; a polyol; acuring agent; and an isocyanate.
 2. The composition of claim 1 whereinsaid bituminous material including a rubber modified oxidized asphalt.3. The composition of claim 1 wherein said bituminous material is a coaltar.
 4. The composition of claim 1 wherein said bituminous material is aperformance graded asphalt.
 5. The composition of claim 1, wherein saidbituminous material is a rubberized asphalt.
 6. The composition of claim5 wherein said rubberized asphalt containing a polymer chosen from thegroup consisting of polyethylene, polypropylene, polystyrene, virginrubber, and crumb rubber.
 7. The composition of claim 6, wherein saidpolymer comprises between five and seventy percent by weight of saidrubberized asphalt.
 8. The composition of claim 1 wherein said polyol isbetween forty and seventy-two percent by weight of said composition. 9.The composition of claim 1 wherein said isocyanate is between five andtwenty percent by weight of said composition.
 10. The composition ofclaim 1 wherein said isocyanate is chosen from the group consisting ofdiphenylmethane diisocyanate, toluene diisocyanate, hexamethylenediisocyanate, and isophorone diisocyanate.
 11. The composition of claim1 wherein said curing agent is between two and eight percent by weightof said composition.
 12. The composition of claim 1, further comprisinga catalyst.
 13. The composition of claim 12 wherein the amount of saidcatalyst is a less than one percent amount by weight.
 14. Thecomposition of claim 13 wherein the amount of catalyst is between oneand five percent by weight of said polyol.
 15. The composition of claim13 wherein said catalyst is chosen from the group consisting ofdibutyltin dilaurate, dioctyltin dilaurate, tertiary amine, andorganometallic compounds of tin, organometallic compounds of lead,organometallic compounds of cobalt, and organometallic compounds ofzinc.